135 



Inelies. 



Length of caudal scute impressions in median line .' . . . , ,-.,-, 2J 



Thickness of plastron at base of anterior, prolongation If 



Thickness of anterior lobe laterally near bottom of axilla 1 



Thickness of posterior lobe near bottom of inguinal fossa 1| 



Thickness of plastron near the center 3 



During a clay's excursion to Dry Creek Buttes, ten miles from Fort Bridger, 

 Mrs. Anna Carter, the wife of Dr. Carter, who accompanied us, discovered a 

 large turtle partially imbedded in a green sandstone on the top of a butte. 

 The upper shield had been destroyed by recent exposure, but the nearly com- 

 plete plastron was obtained by removing the cast of the shell above it. The 

 sutural connections of the bones are somewhat obscured by the firm adherence 

 of particles of sand. It retains the anterior spade-like process nearly entire, 

 and this is represented in Fig. 4, Plate XXX. 



The specimen presents some differences from the former, which, however, 

 I have not regarded as specific, though they may be so. The spade-like pro- 

 longation of the plastron is more abrupt and considerably longer than in the 

 fragment upon which the species was originally founded. The fore part of 

 the anterior lobe of the plastron approaching the lateral border along the 

 groove defining the gular and humeral scute impressions is much more convex 

 than in either of the preceding specimens. From the position of the entoster- 

 num backward, the plastron becomes concave, as in the former specimen, but 

 the concavity is comparatively shallow. The poststernal notch is also of less 

 depth than in the previous specimen, but otherwise the plastron is sufficiently 

 like the latter to pertain to the same species. 



The measurements of the specimen are as follows : 



Inches. 



Length of plastron in median line - 25 



Length of plastron on each side 26i 



Width of plastron at middle, estimated at about 20 



Length of anterior lobe 9 



Length of posterior lobe at middle G 



Length of posterior lobe to ends of angular processes 8J 



Width of anterior lobe at base 12 



Width of posterior lobe at base Hi 



Length of episternal prolongation 2£ 



Width of episternal prolongation at base 5£ 



Width of episternal prolongation near end 43 



Breadth of sternal bridges fore and aft 9 



Breadth at ends of poststernal angular processes li 



Depth of poststernal notch If 



Length of entosternal bone 4f 



Breadth of entosternal bone 5£ 



